refactoring: Refactor the prototype pattern to avoid code duplications (Closes #584) (#1970)

This commit  refactors the Prototype pattern by making it Cloneable and thus inheriting the clone() method to its subclasses which removes code duplications.

Author: yonatankarp

lombok.config

@@ -1,2 +1,2 @@
 lombok.log.fieldName = LOGGER
-
+lombok.addLombokGeneratedAnnotation = true

prototype/README.md

@@ -22,7 +22,7 @@ used for creating new objects from prototype instances.
 
 Real-world example
 
-> Remember Dolly? The sheep that was cloned! Lets not get into the details but the key point here is 
+> Remember Dolly? The sheep that was cloned! Let's not get into the details but the key point here is 
 > that it is all about cloning.
 
 In plain words
@@ -45,24 +45,25 @@ interface with a method for cloning objects. In this example, `Prototype` interf
 this with its `copy` method.
 
 ```java
-public interface Prototype {
-  Object copy();
+public abstract class Prototype<T> implements Cloneable {
+    @SneakyThrows
+    public T copy() {
+        return (T) super.clone();
+    }
 }
 ```
 
 Our example contains a hierarchy of different creatures. For example, let's look at `Beast` and
 `OrcBeast` classes.
 
 ```java
-@EqualsAndHashCode
+@EqualsAndHashCode(callSuper = false)
 @NoArgsConstructor
-public abstract class Beast implements Prototype {
+public abstract class Beast extends Prototype<Beast> {
 
   public Beast(Beast source) {
   }
 
-  @Override
-  public abstract Beast copy();
 }
 
 @EqualsAndHashCode(callSuper = false)
@@ -76,19 +77,15 @@ public class OrcBeast extends Beast {
     this.weapon = orcBeast.weapon;
   }
 
-  @Override
-  public OrcBeast copy() {
-    return new OrcBeast(this);
-  }
-
   @Override
   public String toString() {
     return "Orcish wolf attacks with " + weapon;
   }
+
 }
 ```
 
-We don't want to go into too much details, but the full example contains also base classes `Mage`
+We don't want to go into too many details, but the full example contains also base classes `Mage`
 and `Warlord` and there are specialized implementations for those for elves in addition to orcs.
 
 To take full advantage of the prototype pattern, we create `HeroFactory` and `HeroFactoryImpl`

prototype/src/main/java/com/iluwatar/prototype/Beast.java

@@ -29,14 +29,11 @@
 /**
  * Beast.
  */
-@EqualsAndHashCode
+@EqualsAndHashCode(callSuper = false)
 @NoArgsConstructor
-public abstract class Beast implements Prototype {
+public abstract class Beast extends Prototype<Beast> {
 
   public Beast(Beast source) {
   }
 
-  @Override
-  public abstract Beast copy();
-
 }

prototype/src/main/java/com/iluwatar/prototype/ElfBeast.java

@@ -40,11 +40,6 @@ public ElfBeast(ElfBeast elfBeast) {
     this.helpType = elfBeast.helpType;
   }
 
-  @Override
-  public ElfBeast copy() {
-    return new ElfBeast(this);
-  }
-
   @Override
   public String toString() {
     return "Elven eagle helps in " + helpType;

prototype/src/main/java/com/iluwatar/prototype/ElfMage.java

@@ -40,11 +40,6 @@ public ElfMage(ElfMage elfMage) {
     this.helpType = elfMage.helpType;
   }
 
-  @Override
-  public ElfMage copy() {
-    return new ElfMage(this);
-  }
-
   @Override
   public String toString() {
     return "Elven mage helps in " + helpType;

prototype/src/main/java/com/iluwatar/prototype/ElfWarlord.java

@@ -24,31 +24,24 @@
 package com.iluwatar.prototype;
 
 import lombok.EqualsAndHashCode;
+import lombok.RequiredArgsConstructor;
 
 /**
  * ElfWarlord.
  */
-@EqualsAndHashCode
+@EqualsAndHashCode(callSuper = true)
+@RequiredArgsConstructor
 public class ElfWarlord extends Warlord {
 
   private final String helpType;
 
-  public ElfWarlord(String helpType) {
-    this.helpType = helpType;
-  }
-
   public ElfWarlord(ElfWarlord elfWarlord) {
     super(elfWarlord);
     this.helpType = elfWarlord.helpType;
   }
 
-  @Override
-  public ElfWarlord copy() {
-    return new ElfWarlord(this);
-  }
-
   @Override
   public String toString() {
     return "Elven warlord helps in " + helpType;
   }
-}
+}

prototype/src/main/java/com/iluwatar/prototype/Mage.java

@@ -29,14 +29,11 @@
 /**
  * Mage.
  */
-@EqualsAndHashCode
+@EqualsAndHashCode(callSuper = false)
 @NoArgsConstructor
-public abstract class Mage implements Prototype {
+public abstract class Mage extends Prototype<Mage> {
 
   public Mage(Mage source) {
   }
 
-  @Override
-  public abstract Mage copy();
-
 }

prototype/src/main/java/com/iluwatar/prototype/OrcBeast.java

@@ -40,11 +40,6 @@ public OrcBeast(OrcBeast orcBeast) {
     this.weapon = orcBeast.weapon;
   }
 
-  @Override
-  public OrcBeast copy() {
-    return new OrcBeast(this);
-  }
-
   @Override
   public String toString() {
     return "Orcish wolf attacks with " + weapon;

prototype/src/main/java/com/iluwatar/prototype/OrcMage.java

@@ -40,11 +40,6 @@ public OrcMage(OrcMage orcMage) {
     this.weapon = orcMage.weapon;
   }
 
-  @Override
-  public OrcMage copy() {
-    return new OrcMage(this);
-  }
-
   @Override
   public String toString() {
     return "Orcish mage attacks with " + weapon;

prototype/src/main/java/com/iluwatar/prototype/OrcWarlord.java

@@ -40,11 +40,6 @@ public OrcWarlord(OrcWarlord orcWarlord) {
     this.weapon = orcWarlord.weapon;
   }
 
-  @Override
-  public OrcWarlord copy() {
-    return new OrcWarlord(this);
-  }
-
   @Override
   public String toString() {
     return "Orcish warlord attacks with " + weapon;

prototype/src/main/java/com/iluwatar/prototype/Prototype.java

@@ -23,11 +23,21 @@
 
 package com.iluwatar.prototype;
 
+import lombok.SneakyThrows;
+import lombok.extern.slf4j.Slf4j;
+
 /**
  * Prototype.
  */
-public interface Prototype {
-
-  Object copy();
+@Slf4j
+public abstract class Prototype<T> implements Cloneable {
 
+  /**
+   * Object a shallow copy of this object or null if this object is not Cloneable.
+   */
+  @SuppressWarnings("unchecked")
+  @SneakyThrows
+  public T copy() {
+    return (T) super.clone();
+  }
 }

prototype/src/main/java/com/iluwatar/prototype/Warlord.java

@@ -29,14 +29,11 @@
 /**
  * Warlord.
  */
-@EqualsAndHashCode
+@EqualsAndHashCode(callSuper = false)
 @NoArgsConstructor
-public abstract class Warlord implements Prototype {
+public abstract class Warlord extends Prototype<Warlord> {
 
   public Warlord(Warlord source) {
   }
 
-  @Override
-  public abstract Warlord copy();
-
 }

prototype/src/test/java/com/iluwatar/prototype/PrototypeTest.java

@@ -39,7 +39,7 @@
  * @param <P> Prototype
  * @author Jeroen Meulemeester
  */
-class PrototypeTest<P extends Prototype> {
+class PrototypeTest<P extends Prototype<P>> {
   static Collection<Object[]> dataProvider() {
     return List.of(
         new Object[]{new OrcBeast("axe"), "Orcish wolf attacks with axe"},